Maxim Kuvyrkov wrote:
> The following patch define sigcontext ABI of ColdFire.
...
> --- a/arch/m68k/kernel/signal.c
> +++ b/arch/m68k/kernel/signal.c
> @@ -897,9 +897,15 @@ static void setup_rt_frame (int sig, struct k_sigaction *ka, siginfo_t *info,
>  
>  	/* Set up to return from userspace.  */
>  	err |= __put_user(frame->retcode, &frame->pretcode);
> +#ifdef __mcoldfire__
> +	/* move.w #,d0; trap #0 */
> +	err |= __put_user(0x303c0000 + __NR_rt_sigreturn,
> +			  (long __user *)(frame->retcode + 0));
> +#else
>  	/* moveq #,d0; notb d0; trap #0 */
>  	err |= __put_user(0x70004600 + ((__NR_rt_sigreturn ^ 0xff) << 16),
>  			  (long __user *)(frame->retcode + 0));
> +#endif
>  	err |= __put_user(0x4e40, (short __user *)(frame->retcode + 4));
>  
>  	if (err)

This turned out to be buggy: move.w will only set the lower 16 bits of 
%d0 so if the signal handler leaves something in the high-order bits, 
then the trampoline will trap into a non-existent syscall.  The attached 
patch fixes this; nothing else in it has changed since the initial revision.

I was lured into thinking that the above sequence is OK by m68knommu's 
version of the trampoline.  Arch/m68knommu/kernel/entry.S uses "move 
#__NR_rt_sigreturn,%d0" which assembles into "move.w".  This is too is 
buggy and I'm also attaching the fix for the nommu version.

Regards,

--
Maxim K.
CodeSourcery